The genus Clostridium is composed of anaerobic, spore-forming, rod-shaped bacteria. The organisms occur naturally in soil as well as in the intestinal tract of animals, including man. Pathogenic strains are acquired either by wound contamination or by ingestion. Members of the genus are responsible for a wide variety of diseases which, in the absence of vaccination, cause significant economic losses to the farming industry. Such diseases include red water disease, big head, blackleg, the enterotoxemias, infectious necrotic hepatitis, malignant edema, botulism and tetanus, among others.
Antibiotic treatment of clostridial infections is rarely predictable and often ineffective. Accordingly, such infections are generally controlled prophylactically, using vaccine compositions containing one or more clostridial bacterins or toxoids. See, e.g., U.S. Pat. Nos. 4,292,307; 4,264,588; 3,579,633; Webster, A. C., and Frank, C. L. (1985) Austral. Vet. J. 62:112-114; Kerry, J. B., and Craig, G. R. (1979)The Veterinary Record 105:551-554; Sterne et al. (1962)The Veterinary Record 74:909-913. Clostridial toxoids are soluble proteins of relatively low antigenicity and, traditionally, poor stability. Thus, clostridial vaccines require adjuvants in order to increase antigenic potency and enhance stability. In particular, aluminum compounds, which are capable of adsorbing and/or precipitating clostridial toxoids, as well as retaining the toxoids at the injection site, are typically used. See, e.g., Thomson, R. O., and Knight, P. A. (1976) Develop. Biol. Standard 32:265-269; Thomson et al. (Jul. 26, 1969) The Veterinary Record pp. 81-85. Other potent depot adjuvants, such as water-in-oil emulsions and carbopol, have also been used in clostridial vaccines. The above-described adjuvants, although increasing antigenicity, usually provoke severe persistent local reactions, such as granulomas, abscesses and scarring, when injected subcutaneously or intramuscularly. These local reactions are, in turn, responsible for carcass blemish which requires expensive trimming, a consideration when the vaccine has been injected into muscle tissue destined to be a valuable cut of meat.
Saponins are glycosidic natural plant products, grouped together based on several common properties. The saponins are surfactants, a characteristic illustrated by their tendency to foam when shaken. Saponins are able to lyse red blood cells, form complexes with cholesterol and are toxic to fish. Saponins have been employed as adjuvants in a number of vaccine compositions including vaccines against protozoal infections (U.S. Pat. No. 4,767,622), canine distemper vaccines (U.S. Pat. No. 5,178,862), vaccines against foot and mouth disease, among others. Awad et al. (1986) Assiut Vet. Med. J. 17:201-214 describe a comparison of single component blackleg vaccines including either alum, aluminum gel with saponin or oil adjuvants. However, the use of soluble adjuvants that are readily dispersed from the injection site, and have no depot effect, such as saponin, with a multicomponent clostridial vaccine, has not heretofore been described.